Acid phosphatase enzyme measurements are regularly performed in connection with the diagnosis and treatment of human prostatic cancer. In addition to carcinoma of the prostate, changes in acid phosphatase levels occur in other types of malignant growth, in hairy cell leukemia, in the congenital disorder known as Gaucher's disease, and in a fatal genetic disease characterized by a lack of acid phosphatase. Changes in acid phosphatase levels have also been established in Alzheimer's disease. Despite this, little is known about the structural and catalytic properties, or the biological role, of the diverse group of enzymes known as acid phosphatases. The present project continues an investigation of the fundamental enzymology and protein chemistry of acid phosphatases. The comparative biochemistry, substrate specificity, intracellular location, structure and mechanism of action of two major types of acid phosphatases will be investigated. The first of these is a group of high molecular weight enzymes which have a nucleophilic histidine that is present in a characteristic ArgHisGlyXArgXPro subsequence at the active site. This group includes the important tumor marker human prostatic acid phosphatase as well as human lysosomal and Escherichia coli acid phosphatases. The second major class of enzymes is a group of low molecular weight enzymes (Mr 18,000) that have an active site cysteine nucleophile. These enzymes are active phosphotyrosyl protein phosphatases. The proposed studies include three dimensional structure determinations of the low Mr enzyme by NMR spectroscopy and X-ray crystallography, extensive structure/function studies of both groups of enzymes using site-directed mutagenesis together with spectroscopic and kinetic examinations of the resulting proteins, immunofluorescence and immunoprecipitation studies of intracellular protein localization, and genomic sequencing.